1. Field of the Invention
This invention relates to a coating machine for coating fiber yarns.
2. Description of the Related Art
Referring to FIG. 1, a conventional coating machine 1 includes: a yarn supply device 11 for supplying a fiber yarn 100; a tank 12 spaced apart from the yarn supply device 11 and having a plastisol 101 therein; a molding die 13 disposed adjacent to the tank 12; a drying device 14 disposed spacedly from the molding die 13; and a yarn pick-up device 15.
When the fiber yarn 100 passes the tank 12, it is coated with the plastisol 101. When the fiber yarn 100 passes through the molding die 13, the thickness of the plastisol 101 coated on the fiber yarn 100 is adjusted. Thereafter, the coated fiber yarn 100 is set in shape using the heating device 14, and then, is collected using the yarn pick-up device 15.
Taiwanese Patent No. I332042 discloses a method for coating a fiber yarn 100 (a glass fiber yarn) using a pellet extruder 16 (see FIG. 2). Although coating the fiber yarn 100 by using a plastic material extruded from the pellet extruder 16 is more convenient, when the fiber yarn 100 has a relatively small diameter, it is likely to deform. Besides, it is hard to control the fiber yarn 100 to be centrally located in the coated layer, and thus, the coated layer and the fiber yarn 100 are likely to separate from each other. Furthermore, because the fiber yarn 100 is made of a plurality of filaments, the molding die 13 may be plugged by the fiber yarn 100 when the fiber yarn 100 passes therethrough. Thus, the thickness of the coated layer is hard to control, and more seriously, it may be necessary to shut down the coating machine for repair.
Moreover, after the coated fiber yarn 100 leaves the pellet extruder 16, it is guided and pressed by a roller 17 to be cooled in a cooling water tank 13. Because the coated layer on the fiber yarn 100 is not completely cured, the pressure from the roller 17 will deform the coated fiber yarn 102, resulting in an elliptical cross-section, as shown in FIG. 3. This may adversely affect uniformity and surface evenness of a knitted fabric made of the coated fiber yarn 100.
On the other hand, when the fiber yarn 100 passes through the molding die 13 in the conventional coating machine 1 or in the pellet extruder 16, friction between the molding die 13 and the fiber yarn 100 may result in wear of the molding die 13. In order to lengthen the life of the molding die 13, the molding die 13 is usually made of platinum or diamond. Therefore, the coated fiber yarn 100 made by a conventional method or a conventional machine 1 has a relatively high cost.